1. Field of the Invention
The present invention relates generally to an antenna for use on a missile or the like. More specifically, the present invention relates to a microstrip antenna which includes a GPS conformal antenna which includes a parasitic element for receiving GPS data and which is adapted for use on small diameter devices such as a missile.
2. Description of the Prior Art
In the past military aircraft and weapons systems such as airplanes, target drones, pods and missiles have included flight termination and beacon tracking antenna to monitor performance during test flights. For example, a missile under test will always have an antenna which is generally surface mounted to transmit telemetry data to a ground station. The ground station then performs an analysis of the telemetry data from the missile to determine its performance during flight while tracking a target.
U.S. Pat. No. 4,356,492 is an example of a prior art microstrip antenna which is adapted for use on a missile as a wrap around band to a missile body without interfering with the aerodynamic design of the missile. U.S. Pat. No. 4,356,492 teaches a plurality of separate radiating elements which operate at widely separated frequencies from a single common input point. The common input point is fed at all the desired frequencies from a single transmission feed line.
With the emerging use of the Global Positioning System (GPS) for tracking purposes, there is a need to include GPS within the instrumentation package for a missile and target drone to accurately measure flight performance. GPS data is extremely accurate and thus allows for a thorough analysis of the missile""s performance, as well as the target drone""s performance in flight while the missile tracks the target drone on a course to intercept the target drone.
The use of satellite provided GPS data to monitor the position of a missile and a drone target in flight will require that an antenna for receiving the GPS data be included in the instrumentation package. The receiving antenna should preferably be mounted on the same dielectric substrate as the transmitting antenna so that the antenna assembly can be applied readily as a wrap around band to the missile body without interfering with the aerodynamic design of the missile. Similarly, the antenna assembly which would include a GPS data receiving antenna and telemetry data transmitting antenna configured as a wrap around band to the projectile""s body without interfering with the aerodynamic design of the projectile.
The present invention comprises a GPS conformal antenna which is a wrap around antenna adapted for use on a small diameter projectile, such as a missile. The GPS conformal antenna includes a GPS antenna array of six driven elements mounted on the dielectric substrate and fabricated from etched copper. The six driven elements are microstrip antenna patches which operate as GPS data receiving elements receiving GPS (Global Positioning System) data from an external source such as a satellite.
The GPS conformal antenna also has an antenna cover which includes a parasitic element. The parasitic element which is passive is positioned between two of the six driven elements in alignment with the each of the six driven elements. The electric field coupling between the parasitic element and the driven elements adjacent the parasitic element produces an omnidirectional radiation pattern.